'The Shield' star Kenny Johnson to guest on 'The Mentalist'

The former star of The Shield will guest in a May episode of the CBS drama, reports TV Guide.

He will play Greg Taybeck, the high school boyfriend and ex-fiancé of Lisbon (Robin Tunney).

"She ran away [from that relationship] to find a different life," explained Mentalist creator Bruno Heller. "So, she stops and has to reassess her life and look at the paths not taken. Her boyfriend has kids, and she doesn't. So, how does she feel about that?"

Lisbon will also face a crisis when Taybeck becomes involved in a CBI investigation.

"I think it takes her longer to get to the bottom of the case because it's hard for her to see the thing clearly," said Heller. "But it's her understanding of him and his character that helps solve the case."

Johnson played Curtis 'Lem' Lemansky on FX cop drama The Shield from 2002 to 2007 and has since appeared on Sons of Anarchy and NBC's Prime Suspect remake.

His former Shield co-star Catherine Dent recently played a recurring role on The Mentalist, appearing in four episodes as FBI agent Susan Darcy.